I missed the original post - sounds like homework to me ----- Original Message ----- From: Tippus Tailus To: [email protected] Sent: Thursday, October 19, 2006 4:31 AM Subject: [php_mysql] Re: Query.... in PHP and MySQL
--- In [email protected], Parag <[EMAIL PROTECTED]> wrote: > > Hi, > > I am having some following queries > > 1. What are the modifiers in Smarty in PHP ? No idea. Hopefully, someone else can answer. > 2. What is differenece between Primary Key and Unique Key if we make Unique key as Not Null ? Very good question. Superficially, a PRIMARY KEY is UNIQUE KEY and NOT NULL. However, some storage engines, such as InnoDB, may use an internal numeric primary if no PRIMARY KEY has been defined. For other storage engines, such as MyISAM, it doesn't make much difference. If your schema is normalized then your tables should have primary keys. Otherwise, this distinction will make a bad schema worse because it will further increase storage requirements, decrease row retrieval throughput and decrease cache coherency. In the case of a decomposed relationship between two tables, defining a composite PRIMARY KEY may be beneficial: CREATE TABLE `actor` ( `actor__id` INT UNSIGNED PRIMARY KEY, `actor__dob` DATE, `actor__name` VARCHAR(64) NOT NULL ) ENGINE=INNODB; CREATE TABLE `film` ( `film__id` INT UNSIGNED PRIMARY KEY, `film__name` VARCHAR(250) NOT NULL ) ENGINE=INNODB; CREATE TABLE `role` ( `film__id` INT UNSIGNED NOT NULL, `actor__id` INT UNSIGNED NOT NULL, `role__character` VARCHAR(64) NOT NULL ) ENGINE=INNODB; ALTER TABLE `role` ADD PRIMARY KEY (`film__id`,`actor__id`); > 3. What is Versioning ? What Freeware or Shareware Softwares used for Versioning ? Versioning in databases is different to versioning in software such as CVS [Concurrent Versions System]. When you have concurrent transactions, it is very useful for each session to see the state of the database as is was when a transaction began. This requires holding old versions of rows until transactions commit or rollback. > 4. What is PHP - Documentor ? is it supported in PHP 4.x version ? No idea. > 5. What is funda of callback function and in what situation we use call back function in PHP and Javascript ? Callbacks in programming languages are used when you're working at a level below object orientation. It allows a specified routine to be called from a generic library. Examples include sorting and enumeration. In the case of sorting, you may a library routine, such as the POSIX qsort(...) which is very efficient and may be optimized for particular hardware. This library function can call the routine of your choice allowing the comparison of two arbitrary pieces of data. This would allow you to sort numbers, names, pictures and colors to your precise requirements. A programming callback gives you precision and speed. It allows you to draw upon the expertise embodied in libraries. In general, callbacks, trampolines, virtual methods and enumeration is heavy mathematical and programming theory. Investigate enumeration in SmallTalk for more information. Callbacks in JavaScript are used for AJAX trickery and are generally techniques for making hits on a web server to fetch new information. Firstly, any reference you've seen in PHP documentation about callbacks is completely unrelated to callbacks in AJAX. Secondly, defer these techniques until you've got a working application. It is quite simple to retro-code these improvements. To consider them in version 1 complicates your project and risks its entire failure. > 6. what is use of mysqli ? is it faster than normal mysql ? > how it increases speed of query when we use mysqli - extension than normal mysql functions available in php? (As we r using extension but i think there will same mysql functions used ) MySQL Server 5.0 allows the use of stored procedures. Stored procedures may return multiple result sets. In PHP, mysqli_* functions handle multiple result sets mysql_* functions don't. If you want to use stored procedures effectively then you'll have to use mysqli_* . > 7. what should be done if there r more hits to mysql server as because of that it is delaying transcations processing ? what can be done to stream line this ? That's a very good question. You can configure your webserver to reduce the maximum number of concurrent connections and vastly increase the TCP listen buffer so that connections are not refused. You'll probably want to change settings anyhow. For example, Apache's default number of maximum connections is 150. MySQL Server 5.0's default number of maximum connections is 100. This is one reason that relatively busy websites occasionally display warnings about connection problems. > 8. when we give request to particular page - (we r using session) how server understand some specific value is to be displayed for particular session ? I want to know how it internally works (when we send request from browser- client to server) ? (any information sent like session id or something like that ? > > 9. how the hackers generally logs in remote site then ? i want to log in remote site which is not mine - how to find what cookies and session variables are created ? There are a variety of methods to implement sessions. I'm most familiar with writing my own in Perl and I haven't done PHP sessions for about five years. Popular methods include adding a session= parameter or suchlike to Method GET URLs and setting cookies. Not everyone want to share cookies and this is understandable because this facility is widely used by advertisers to abuse privacy. If you want to see this in action then enable the most paranoid cookie confirmation settings in your web browser. Firefox is good for setting appropriate security levels and displaying collected cookies. Method GET parameters also have weaknesses. For example, if a URL with a live session is shared between users then the session (and account) can be hi-jacked. Thankfully, there are functions and libraries which allow URLs to be selectively re-written to include session information as a Method GET parameter in the event that a cookie doesn't work. > 10. how index internally works ? > for ex. when searches like > - select * from employee where name like '%par' - i want to compare first 3 characters of field > - select * from employee where name like 'par%' - i want to compare last 3 characters of field > which query is will take more time if i done indexing on name field - because i am comparing first 3 and last 3 characters If we use the following table and index as an example: CREATE TABLE `user` ( `user__id` INT UNSIGNED PRIMARY KEY, `user__name_title` CHAR(8), `user__name_first` CHAR(32), `user__name_middle` CHAR(32), `user__name_last` CHAR(32), `user__name_suffix` CHAR(16) ) ENGINE=MYISAM; ALTER TABLE ADD INDEX `name` (`user__name_last`,`user__name_first`,`user__name_middle`); Then we implicitly get three indexes: (`user__name_last`,`user__name_first`,`user__name_middle`); (`user__name_last`,`user__name_first`); (`user__name_last`); So, we can efficiently search last name only; first name and last name; and first, middle and last name together. We can also efficiently perform the following: SELECT ... WHERE `user__name_last` LIKE 'Smith%'; However, it doesn't help any other pattern or subset of columns. In these cases, the database will perform a full table scan unless you create additional indexes. For small quantities of data, it doesn't matter. For larger amounts of data, you can find problematic queries in the slow query log. Finally, UNIQUE doesn't apply to NULL. Try to avoid indexes on NULL values by normalizing. > 11. what different types of indexes available in mysql ? what r there use and internal working ? There are hash indexes. These are useful if you don't want to compare values or select a range of values. These are ideal for primary keys. There are B-trees. These are useful for finding alphanumeric prefixes or numeric ranges. There are T-trees. These are useful in in-memory databases, such as MySQL NDB Cluster, where the access speed of memory is significantly faster than disk. There are R-trees, which are two dimensional indexes useful for geographic data. There are probably other indexes. Different storage engines support a different subset of indexes. > 12. I want to submit page not using <form> tag - > how can i decide which method to choose - fsock / curl / snoopy class - or is there any other method than (Except javascript ). You may be lacking abstraction here. When you're editing source files, you've probably got a jumble of CSS, JavaScript, HTML, PHP and SQL. Don't do this. Put your CSS and JavaScript in separate files. Put your SQL queries in separate files. Put your application logic in separate files. Your HTML should have a minimal amount of PHP - just enough to reference your application logic, which in turn references your SQL routines. When the processed HTML is sent to a client, it collates the references to the CSS and JavaScript as appropriate. Your JavaScript runs on the client and your PHP runs on the server. When you abstract style, HTML, application and SQL then the separation is more defined. When you've incorrectly got everything in one file then it encourages woolly thinking - such as having CURL (in PHP on the server) submitting data like JavaScript (on the client). If you want to do DHTML, DOM and AJAX trickery then you are strongly advised to first separate your CSS, JavaScript, HTML, PHP and SQL. The current state is not your fault. The structure of PHP, ASP and similar languages encourages this mess. To fix it, try the following: <Script Language="JavaScript" Src="index.js"></JavaScript> <?php include 'library/app.php'; include 'library/db.php'; ?> > 13. when we create more than one fields how mysql server decides about which index to use for sorting records ? A suitable composite index will be used if it is present. Additionally, the cardinality of indexes will influence the order of retrieval from tables. > 14. What is use of CURL ? CURL allows applications to initiate network connections using a variety of protocols. This facility is ideal sourcing and submitting data to third parties, including third party credit card gateways, newsfeeds, weather reports, remote server status monitoring, authentication services, search services and abstraction within your application. The latter is particularly useful. For example, if you want to write an application which works on web browsers (HTML), mobile telephones (WAP) and desktops (XML) then you can write the core of your application as a web service and then provide skinned output for each interface. For example, a web service for searching may output the following: <SearchResultSet> <SearchResult Res="00012345" Name="Fun With PHP"> <SearchResult Res="00012346" Name="Fun With MySQL"> </SearchResultSet> You then write PHP which uses CURL to obtain this data and then output the following HTML: <OL> <LI><A HRef="?action=view-res&res=00012345">Fun With PHP</A> <LI><A HRef="?action=view-res&res=00012346">Fun With MySQL</A> </OL> The output for WAP may be completely different. For example, the WAP output may have significantly less style. The alternative to web services is a technique known as screen scraping. This is vastly less preferable and still requires facilities such as CURL. > Please let me know if u know these answers of any questions. > > Quick Reply is definatly Appreciated > > Regards, > > Parag > > > Rgds, > > Parag Bhavsar Tippus Tailus [Non-text portions of this message have been removed] The php_mysql group is dedicated to learn more about the PHP/MySQL web database possibilities through group learning. Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/php_mysql/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/php_mysql/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
